In recent blog article on friction, I discussed about a new Abaqus functionality that allows user to define friction as surface property and Abaqus computes contact pair friction coefficients from corresponding surface friction properties. In this blog article we discuss yet another nice and recent functionality in Abaqus explicit called anisotropic friction.

The anisotropic behavior may arise from number of scenarios the most common of which is composite material that has longitudinal and transverse fiber directions. In such a scenario, the coefficient of friction between contact pair depends on the relative direction of sliding between the contact surfaces. Looking for a real-life example!!!

“The interaction of seat belt with the occupant body is an example of anisotropic friction”

he above figure shows the concept pictorially. Blue arrows indicate the direction of relative sliding. Hence these arrows are always at an angle of 180 degrees. The red lines show the direction of primary material axis. Theta is the angle between blue arrows and red lines per surface. The directional friction stress is computes as:

Both anisotropic friction as well as estimation of friction interaction from surface property are in the category of “combinatorial rules” and both are controlled by same keyword entry as follows in the .inp file.

If both the nominal friction and directional preferences are to be determined from surface property, it is not necessary to define *friction keyword.